Ground Source Heat Pumps
Ground source heat pumps use pipes buried in the garden to extract heat from the ground. This is usually used to heat water for radiators, underfloor heating systems and hot water.
Beneath the surface, the ground stays at a constant temperature, so a ground source heat pump can be used throughout the year - even in the middle of winter.
How does a ground source heat pump work?
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe - called a ground loop - which is buried in the garden. Heat from the ground is absorbed into this fluid and is pumped through a heat exchanger in the heat pump. Low grade heat is then extracted by the refrigeration system and, after passing through the het pump compressor, is concentrated into a higher temperature useful heat capable of heating water for the heating and hot water circuits of the house. Ground loop fluid, now cooler, passes back into the ground where it absorbs further energy from the ground in a continuous process while heating is required.
The length of the ground loop depends on the size of your home and the amount of heat you need - longer loops can draw more heat from the ground.
Normally the loop is laid flat, or coiled in trenches about two metres deep, but if there is not enough space in your garden you can install a vertical loop to a depth of up to 100 metres for a typical domestic home.
Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally.
The efficiency of a ground source heat pump is measured by a coefficient of performance (CoP) - the amount of heat it produces compared to the amount of electricity needed to run it. A typical CoP for a ground source heat pump is around 3.2 if used with under floor heating (it can be reduced if used with radiators). This means for every unit of electricity used to power the pump, you could get 3.2 units of heat.
The benefits of ground source heat pumps
- Reduce your CO2 emissions: on average a ground source heat pump could save around 540kg of carbon dioxide every year when replacing an oil boiler. Emissions can be reduced further ifthe heat pump is partly powered by another renewable technology, such as solar electricity (PV).
- No fuel deliveries required.
- Can provide space heating and hot water
- Can lower fuel bills, depending on what heating fuel you are replacing
- It's often classed as a ‘fit and forget’ technology because it needs little maintenance.